Petroleum geology

A great variety of proven hydrocarbon plays and trap styles is present in the sedimentary succession in the subsurface of the Netherlands. This sedimentary succession started to develop in the middle Paleozoic and has been deformed by several periods of tectonic structuration. In much of the subsurface, the thick Permian Zechstein salt provides an effective seal between a prolific Paleozoic gas system and a mixed, oil and gas-prone Mesozoic hydrocarbon system. The dominating Rotliegend play is formed by a near-ideal superposition of i) a thick upper Carboni ferous (Westphalian) succession with abundant coal measures as the source rocks for gas, ii) well developed fluvial and eolian reservoir sandstones of the Permian Upper Rotliegend Group, and iii) the excellent seal of the Zechstein salt. The giant Groningen field is by far the largest representative of this play and represents two thirds of the total recoverable Dutch gas reserves, containing an initial recoverable gas volume of ca. 2800 x 109 m3. Production of the Groningen gas was very profitable for decades, but eventually the impact of production induced seismicity resulted in a premature cessation of production. Triassic plays are second in importance with respect to proven gas accumulations. Relatively minor gas reserves occur in Permian Zechstein carbonates, Upper Jurassic and Lower Cretaceous sandstones, Upper Cretaceous chalk as well as in shallow, unconsolidated sands of Cenozoic age. Producible oil occurs within Upper Jurassic and Lower Cretaceous rift-basin sediments in a variety of sandstone reservoirs and trap styles. Minor amounts of oil have also been produced from the Upper Cretaceous chalk and the Triassic sandstones. The exploration of the Dutch hydrocarbon plays is in a mature stage and many of the current gas fields will be depleted in the next decade. The urge for energy transition is growing and moreover diminishing public acceptance is restricting exploration and production activities. Consequently, exploration and production are concentrating on the offshore area. The role of fossil fuels in the energy system will decrease significantly in the coming decades and is expected to cease (almost) completely in 2050.